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Development Dual Stream header pays dividends

New Holland’s Dual Stream knife system has the potential to boost combine output simply by reducing the volume of crop entering the harvester. Geoff Ashcroft spoke to a Gloucestershire grower about its performance.

Few harvesting innovations have focused on reducing the volume of straw going into a combine. Less straw means easier threshing along with the potential for more output – all without need to change combine or working width.

The Shelbourne stripper header was one such innovation, but the standing straw it left behind required an altogether different approach for cultivation work. It also required a rethink for those seeking to bale.

Now it is New Holland’s turn, with the arrival of the Dual Stream knife. It too, is designed to reduce the amount of material entering the combine. And what started as a post-graduate university project in Germany to improve combine output is now being evaluated in the UK ahead of a limited production run for 2016.

Dual Stream appears to be a straightforward solution. Essentially a twin knife header, it employs a second knife at the back of the table, which floats independently of header height.

This allows the combine’s primary knife to be used much higher - typically 10-20cm above traditional cutting height. Doing so reduces the amount of crop taken into the combine, leaving the second knife to trim remaining stubbles to a manageable height.

Unlike previous header solutions, this latest development can integrate with a farm’s existing harvesting and cultivations regime, without need for additional processes.

Prototype

Richard Ward (pictured), farms manager at The Barton Farms, Moreton in Marsh, Gloucestershire, has been using a prototype Dual Stream knife with a 7.65m Vari-feed header for the last three seasons to harvest the farm’s 242ha of combinable crops. Fitted to his CX6080 combine and replacing the standard 6.1m header, he says the introduction of Dual Stream has boosted throughput considerably.

“Without Dual Stream, our CX will harvest around 25 tonnes/hour in wheat,” he says. “With Dual Stream, this output has grown by 50 per cent, to 37.5 tonnes/hour.”

“We’re travelling much faster, so harvesting times are reduced and this gives us a significant fuel saving too,” he says.

All of which is a direct result of reducing the volume of material going into the combine.

“A 10 tonne/ha crop of wheat will contain around 10 tonnes/ha of straw – if we’re only taking in seven or eight tonnes of straw, it stands to reason that we can travel much faster.”

In oilseed rape, he says the performance gain is much greater and can typically be up to 100 per cent more output.

“We can now harvest up to 80 acres of rape/day, instead of 40 acres,” he adds.

He says that the limiting factor with the farm’s CX6080 was the straw walkers’ ability to process material. By reducing the volume of straw going over the walkers, he says the flow restriction has been removed, and this enables the sieves to do more work.

“Dual Stream means we can now make the sieves much more productive,” he says. “We can open the sieves further and run more airflow. This has given us more output.”

“We no longer get straw walker losses, so I can now set the combine by sieve losses and the returns elevator. And our sample quality has remained unchanged.”

Extra capacity

All this extra productivity also allowed The Barton Farms to enter a labour and machinery sharing partnership with a neighbouring farm, which has provided a further 162ha of combining.

During harvest, Mr Ward sets the Dual Stream knife to leave a finished stubble height of about 10-11cm. He can vary the working height of the primary knife by lifting and lowering the header to suit the crop, but typically, it is 10-15cm higher than the finished stubble height, depending on the crop.

He accepts that by cutting high, the farm is effectively losing 15-20 per cent of its straw production, but he notes that the quality of straw has increased dramatically.

“Because we are leaving the lower part of straw behind, and this is often greener, wetter material, the moisture content of straw is now much lower,” he explains. “Much drier straw has a far higher absorbency value, so our customers use less to house cattle.”

“And by not taking greener material though the combine, our grain moisture content is also improved by about 0.5 per cent when it comes off the combine,” he says.

Key to effective straw management comes from cage-type rollers behind the Dual Stream knife. Like the combine’s tyres, these press the trimmed straw and remaining stubble to make incorporation much easier.

The trimmed straw and stubbles in the central area of the combine are not rolled, but left untouched so it supports the main volume of straw that is deposited for baling. Mr Ward says the weight of straw in the swath also has the effect of pushing the trimmed material closer to the field surface.

When chopping straw, he says the force of chopped material leaving the combine is enough to blast material onto the surface – again, to ease incorporation.

While there appear to be no disadvantages, there are some crops where Dual Stream offers no tangible benefit. For example peas and beans, where pods can sit low to the ground.

“In our experience, Dual Stream works better in taller crops such as wheat, barley and oilseed rape,” he says.

What is Dual Stream?

New Holland’s Dual Stream system uses a secondary knife mounted to the back of a Vari-feed header. This allows the combine to cut much higher and harvest a reduced volume of material, while leaving the secondary knife to trim remaining stubbles to a manageable height.

The secondary knife is carried on cage rollers which determine its cutting height. This means the knife can float independently of the header, and the rollers press the cut material to simplify incorporation of residues.

Operating at a much higher cutting height than usual means greener straw and weeds can also be left behind. This reduces the risk of wetter material increasing grain moisture content when passing through the combine.

New Holland’s harvesting specialist Nigel Honeyman says that such a system reduces loading on the primary knife, intake auger and fingers. And using the header to leave a taller stubble means there is less likelihood of stones and foreign objects making their way into the combine too.

A reduced crop volume going into the combine also means greater throughput, and an increased forward speed which leads to shorter harvest times.

Without electronics, the mechanically driven knife only needs hydraulic feed for its lift rams and a pto input – the latter is standard on larger New Holland combines and optional on mid-sized and TC models through the use of a maize header drive kit. The power requirement is said to be 4hp on a 7.62m (25ft) header.

Dual Stream can be retro-fitted to any New Holland Vari-feed header with cutting widths of 7.62, 9.14, 10.67 and 12.5m (25, 30, 35 and 41ft), though longer term it is expected that the system could become available to fit any combine header.